Semiautomatic turret lathe



Oct. 27, 1953 c. E. GREENE ET AL 2,656,589

I SEMIAUTOMATIC TURRET LATHE Filed March 2, 1948 I5 Sheets-Sheet 1 IN VEN TORS ROBERT B. LESHER CLAUDE E GREENE c. E. GREENE ET AL 2,656,589

SEMIAUTOMATIC TURRET LATHE Oct. 27, 1953 3 Sheets-Sheet 2 Filed March 2,1948 2c, CTIFIER INVENTORS ROBERT B. LESHER CLAUDE E. GREENE Oct. 27,1953 Q GREENE ETAL Q 2,656,589

SEMIAUTOMATIC TURRET LATHE Filed March 2, 1948 3 Sheets-Sheet 3 LKEE a f0 o I 0 Q I INVENTORS ERT B. L ER UDE E. G NE BY Patented Oct. 27, 1953SEMIAUTOMATIC TURR-ET LATHE Claude E. Greene and Robert B. Lesher,Sidney, Ohio, assignors to The Monarch Machine Tool Company, acorporation of Ohio Application March 2, 1948, Serial No. 12,586

13 Claims.

The invention relates in general to a turret lathe which is adapted tohave a high speed of operation.

An object of the invention is to provide a high speed operating turretlathe wherein all controls are mounted on a small control panelconvenient to the operator of the lathe.

Another object of the invention is the provision of a turret lathehaving a very small set up time by electrical controls.

Another object of the invention is the provision of a turret lathehaving quick indexing between the faces of the turret and a very smallelapsed. time for the total cycle of operation on a given workpiece.

Another object of the invention is the provision of a turret lathehaving a control panel which includes all electrical controls of thelathe and with a surface speed indicator mounted on the control panelfor continually indicating the surface cutting speed of the workingdiameter of the workpiece.

A further object of the invention is the provision of a turret lathehaving variable and reversible spindle speeds in all positions of theturret and having a switch rotated in accordance with the position ofthe turret which switch has an additional contact between each face ofthe turret to provide for relieving the reverse spindle rotation in anyturret position.

A still further object of the invention is the provision of a turretlathe having electronic rectifiers for supplying each the armature andfield of the spindle motor and an electronic rectifier supplying energyto the feed motor for the saddle.

Yet another object of the invention is the provision of a turret lathehaving rectifiers for the spindle and feed motors with continuallyadjustable spindle speeds in each of the positions of the turret withdynamic braking of the spindle motor to a pre-determined speed betweeneach of the indexable positions of the turret.

Other objects and a fuller understanding of the invention may be had byreferring to the following description and claims, taken in conjunctionwith the accompanying drawing, in which:

Figure 1 and Figure 2 show the electrical control system fora turretlathe;

Figure 3 is a combined schematic diagram of the circuit for the surfacespeed indicator and a plan view of the turret lathe; and

Figure 4 is an elevational view of a control panel on which is mountedall the electrical controls for the turret lathe.

The invention is an improvement over the application of Claude E.Greene, Serial No. 642,906 entitled Turret Lathe, and filed January 23,1946, now Patent No. 2,587,312, granted February 26, 1952.

The invention is directed specifically to the improvement of turretlathes wherein high speed of cycling, fast set-up time and convenienceto the lathe operator are all accomplished in one machine. Such a turretlathe may be as shown in the plan view of Figure 3. This turret lathe His shown as including a saddle l2 on which is mounted a multi-facetturret l3 which, in this case, is shown as the conventional six-sidedturret. The saddle |2 is adapted to be reciprocably moved by a capstanl4 along ways 15. A cross slide I6 is adapted for transverse movement ofthe ways |5 by the actuation of the cross slide capstan H. A spindle I8is adapted to hold the workpiece l9 which may be conveniently fedthrough a hollow spindle shaft 20. A rotary tap switch 2| is adapted tobe rotated in accordance with the rotative position of the turret l3 andis used for the control of the electrical circuit which energizes thespindle motor 22 and feed motor 23.

Figure 4 shows a control panel on which are mounted all of the manuallyoperable electrical controls of the electrical circuit shown in Figures1 and 2. The electrical circuit shown in Figures 1 and 2 includes thespindle and feed motors 22 and 23, an armature rectifier 24 forsupplying rectified energy to the armature 25 of the spindle motor 22, afield rectifier 26 for supplying rectified energy to the field 21 of thespindle motor 22, a feed motor rectifier '28 for supplying rectifiedenergy to the feed motor 23, and a control rectifier 29 for supplyingrectified energy to a control circuit indicated generally by thereference character 30. The rectifiers 24, 26, 28 and 29 are adapted tobe supplied with alternating current energy from an alternatingglzirrent source 3| as controlled by a main switch The control circuit30, which may be considered as including so much of the circuit as isshown in Figure 1, includes in general the rotary tap switch 2| andcontrol relay means 33. The rotary tap switch 2| is adapted to haveswitch contacts of a number equal to twice the number of faces on theturret l3, which in this case will be the twelve tap contacts 35 to 46inclusive. rhe odd-numbered contacts 35, 31, 39, 4|, 43 and 45correspond to the faces of the turret l3. In other words, theseodd-numbered tap contacts are adapted to be 4T, 48, 45, 5B, 5! and 52.These first tosixth re lays inclusive are adapted to be "energized uponthe actuation of the correspondingodd-numb d tap contact. The controlrelay means 33 also cludes a reverse tapping relay 51a cross slide inrelay 54, a cross slide out relay 55 and first, sec

nd and third time delay relays 55, i'and58 respectively. The first relay4i has four normally open contactors illi, B, C and '1), Likewise, thesecond to sixth relays 4.8, to 52 have four-normally' open contactors Ato Dinclusive. The, reverse tapping relay has four normally opencontactors 53A, B, C and D and a normally closed contactor 53E. Thecross slide in relay 56. has four nor mally open contactors 54A, to 55Dinclusive. The cross slide out relay 55 has four normally opencontactors 55A to 5513 inclusive.

The first time delay relay 5,5. has three normally open contactors 55A,3 and C, and normally closed contactor 55D. The second time delay relay5l' has three normally open contactorsf em, B and. C, and a normallyclosed contactor 5?]3.

The third time delay relay 58 has one normally closed contactor 58A.

The alternating current source energizes the control circuit 36 by leads59 and through the main switch 32 with the control relay means 33 beingoperablefrom alternating current. The control rectifier 29 suppliesrectified current through the leads 6i and '52 to a further portion ofthe control circuit 3 A master switch 63 is inserted in the lead SI andcontrols the'entire operation of the lathe. may be mounted ina'convenient location such as on the control panel ttshown in Figure 4or preferably mounted in a convenient location on the headstock 65 ofthe lathe H where it is readily available forstcpping the lathe in anyemergency. A -forward relay 6% and a reverse relay 6'5 are adapted'to beenergized from the control rectifier 29 through the lcadst! and 62. Theiorward and reverse relays :36 and 3? each have five contactors A to85123, inclusive, the contactors A, D and .13 being normally open, andthe 'contactors B and C being normally closed.

Manual switch means $8 are provided to accomplish forward or reverserotational direction of the spindle motor 22 and hence the spindle [8 inany of the'operative positions of the turret i3 or the cross slide in orout positions. The manual switch means '58 includes first to sixthmanual switches 69 to 14 inclusive, a reverse tapping switch 75, a crossslide in switch TE and a cross slide out switch "5?. These manualswitches may" be conveniently mounted on the control panel 6 3. Thesemanual switch means 68 which include the switches 69 to al inclusive areall shown as being single polefdouble throw switches which in the upperposition are adapted to energize'the forward relay through a forwardlead; Stand when in the lower position, to energize the reverse re-J lay61 through a reverse lead 9|. 'Such'energization of either forward orreverse relays E5 and This master switch 83.

6! provide corresponding rotational directions of the spindle motor 22.These manual switches 69 to T1 are each respectively connected in serieswith a normally open contactor having the suffix A of the correspondingrelay 4! through 55 of the control relay means 33.

One side of the forward and reverse relays 66 and 5'! are connectedtogether by a connecting link 18. In series with these paralleledforward and reverse relays 85 and 61, is a first holding res'istor 19.This first holding resistor 79 has a resistance value, srnlioient toprevent pull in of eitherthe forward or reverse relays E6 and 61 uponsubjection of; this series combination to the control voltage from thecontrol rectifier 29, and

having a resistance value insuificient to cause dropout of either theforward or reverse relays 66 and C after the energization and pull in ofone of said forward or reverse relays 55 and 6?.

The leads 6! and 62 of the control rectifier 29 are, alsoadaptedtoenergize a braking control relay BJand field accelerating relay8 l. The braking control relay 8G is connected in series with theparalleled combination of the forward and reverse relay contactors 55Aand 57A, which contactors are normally open. The braking control relay80 is then energized by the closing of either of these forward orreverse relay contactors 65A or 61A.

The field accelerating relay 8i has a shunt coilv 82 and a series coil63 mounted on the same core. The shunt coil 82 is for the purpose ofenergizing this field accelerating relayflj to a certain degree. shortof pull in of this relay 8,l. The series coil, 33 is adapted undercertain conditions to provide additional energization to this fieldaccelerating relay 8| to cause pull in thereof. A single normally opencontractor 81A is provided for this field acceleratingrelay 8|. Acurrent limiting resistor 84 is connected in series with the shunt coil820i the field accelerating relay 8! to limit the current below the pullin point of this field accelerating relay 5! as aforementioned.

The control relay means 33 is adapted to be energized from the leads 59and 50. Energizing current for the first to sixth relays ll to 52 isprovided between leads 59 and a lead 85. This lead dais energizedthrough a contactor of each of the reverse tap relay 53 and the firstand the second. time relays 56 and 5'! with reference characters 53E,58A and 57A respectively. The time delay relay contactors 55A and 51Aare normally open contactors and the reverse tapping. relay, contactoris a normally closed contac tor. The reverse tapping relay 53 isconnected, between the leads and 60 through a normally closed time delayrelay contactor 53A and a normally openreverse tapping relay contactor53D., The reverse tapping relay 53 may also be energized upon theactuation of a reverse pick up switch 35. This reverse pick up. switch86, is shownas a single pole.v double throw switch normally in the lowerposition and adapted to be actuated to the upper. position by the travelof the saddle 22 to the completely forward position. This reversetapping relay 53 may hence, as its name impliesbe used to reverse thedirection of the spindle motor 22 after a tapping operation so that thework may be backed off the tap. The. first time delay relay 5G. isconnected between the leads 59 and 59, with a cross slide in switch 81and the lower contact of the reverse pick up switch 8%; connected inseries with this first time delay relay 5E. Ina like fashion, thesecond. time delay relay 5'! is serially connected through the lowercontact of the reverse pick up switch 86 and a cross slide out switch 88between the leads 56 and E0. The cross slide in and out switches 8"! and86 are single pole, double throw switches normally in the upper positionto cause energization of the first and second time delay relays 56 and51 respectively. The lower contacts of these cross slide in and outswitches 81 and 88 are connected to a lead 89 for providing energizationof the third time delay relay 58.

The even-numbered tap contacts 36, 38, 40, 42, 44 and 46 are likewiseconnected between the lead 59 and the lead 89 to provide energization ofthis third time delay relay 58 upon the actuation of any of theseeven-numbered tap contacts. The cross slide in and cross slide outrelays 54 and 55 are connected between the leads 66 and 69 with normallyclosed time delay relay contactors 55D and 51D in series therewith,respectively.

It will be noted that the manual switches 69 through I5 have only onecontactor of the corresponding relay in series therewith. The manualswitches l8 and ll, namely the cross slide in and out switches, havethree normally open contactors in series therewith with this seriescombination connected across the lead 6| and the forward lead 80, or thereverse lead 9|. The three contactors in series with the cross slide inswitch I6 are the two cross slide in contactors 54D and 54A and thecross slide out contactor 55D. The three contactors in series with thecross slide out switch TI are the first time delay relay contactor 560,the second time delay relay contactor 51C and the cross slide outcontactor 55A. Connecting leads 92 and 93 are used to interconnect theseries combination of these three contactors between each successivecontactor.

Figure 2 shows generally the energization circuits for the spindle andfeed motors 22 and 23. The rectifiers 24, 26 and 28 which supply energyto these spindle and feed motors 22 and 23 are adapted to be controlledin speed by a plurality of variable potentiometers. These potentiometersare manually adjustable and may be mounted on the control panel 64 forease and convenience to the operator. Field potentiometer means 94 areprovided for varying the voltage output of the field rectifier 26 with aseparate control potentiometer for each of the six positions of theturret I3, the reverse tapping condition and the cross slide in and outconditions. These field potentiometer means are designated by referencecharacters 95 to I03 inclusive, and are connected in parallel acrosscontrol leads I I5 and H6. The armature rectifier 24 is also adapted tohave variable voltage output conditions for each of the variousoperating conditions of the lathe I I with the voltage output beingcontrolled by armature potentiometer means I04. The armature rectifier24 has two control leads H"! and H8 across which variable resistancesmay be connected to provide varying amounts of output voltage of thearmature rectifier 24 as supplied to the armature 25 of the spindlemotor 22. The armature potentiometer means H14 includes potentiometersI05 to H3 inclusive, which correspond respectively to the six operatingconditions of the turret I3, the reverse tapping condition and the crossslide in and out conditions. These armature potentiometers are connectedin parallel across the control leads II I and H8. The fieldpotentiometers and armature potentiometers corresponding to the sameoperating condition of the lathe are connected together by linking means34 for simultaneous and comple- .mentary actuation. As is well known, toprovide variable speeds of a direct current shuntmotor, both below andabove base speeds, the applied armature voltage should first be raisedfrom 0 to 100 per cent rated value with full field voltage, thendecreasing the field voltage while maintaining rated armature voltage toprovide speeds above the base speed of the motor. In accordance withthis type of operation, the field and armature potentiometers are sointerlinked as to provide for first increasing the armature rectifieroutput voltage and then decreasing the field rectifier output voltage.This provides for single control of the speed of the spindle motorthrough a continually variable range from 0 to some percentage abovebase speed, such as 200 per cent. This single control may be shown asbeing effected by the control knobs H4 on the control panel 64.

The rectifiers 24, 26 and 28 may be of the conventional type shown inthe afore-mentioned patent of Claude E. Greene wherein thepotentiometers are used to bias an arc discharge device such as athyratron and wherein the minimum amount of resistance inserted in thecircuit provides for the maximum output voltage. Connected across thecontrol leads H5 and H6 of the field rectifier 26 is the normally openfield accelerating relay contactor BIA thus providing full outputvoltage of the field rectifier 26 to the field 21 upon energization andpull in of this field accelerating relay Bl. Also connected across thecontrol leads H5 and H6 are the normally closed forward and reversecontactors B6B and 6113 in series to thus provide full output voltage ofthe field rectifier 26 upon deenergization of both the forward andreverse relays 66 and 61. The field potentiometers 95 to I83 are eachconnected in series with the corresponding normally open contactor ofthe respective relay of the control relay means 33 across the controlleads H5 and H6. Likewise, the armature potentiometers I65 through I I3are connected in series with the corresponding normally open contactorhaving a sufiix C of the respective relay of the control relay means 33across the control leads Ill and H8.

The armature rectifier 24 has two output terminals H9 and I20 forsupplying the variable voltage to the armature 25. Forward and reverserelay contactors 66D and 66E, 61E and 61D are provided in the leads tothe armature 25 for reversing the energization thereto and hence therotational direction. Connected in series in one of the leads to thearmature 25 is the field accelerating relay series coil 83. Connectedacross the armature 25 is a series combination including the normallyclosed forward and reverse relay contactors 66C and 610 and a dynamicbraking resistance I2 I. Also connected across the armature 25 is theseries combination of a braking relay I22 and a second holding resistorI23. Shunted across the second holding resistor I23 is a normally openbraking control relay contactor A.

The feed motor 23 obtains its energization from the feed motor rectifier28. This feed motor rectifier 28 is controlled by resistance connectedacross control leads I24 and I25 in similar fashion to the control ofthe field and armature rectifiers 26 and 24. Feed motor potentiometermeans I26 is provided to vary the resistance connected across thecontrol leads I24 and I25. The feed motor potentiometer means l-261includes reed motor potentiometers; I141.

through I32 which control the voltage output supplied to. the seriesfeed motor 23 in accord.- ance with the control: established by thecontrol relay means. 33; Each. of the feed. motor potentiometers. I21through I32 is connected in; series and provide for dynamic braking ofthe feed.

motor 23. upon de-energization of' the feed motor relay i2? The feedmotor 23 has an armature I36 and a field- I31 which upon thedynamicbraking condition are connected in serieswith the field I31 connected ina reverse manner relative to the running condition. A feed brake relayI38 is connected across the armature I36;and has one normally closedcontactor IfiilA. This feed brake contactor IEGA is shownin Eigure l as:being connected'in series with-the feed motor relay I35, and the firstand second;time delay relaycontactorsStB and 57B. This seriescombination. is connected between the. lead 62. and the forward lead 96.Shunted across the feed brake contactor I38A is a third holding.resistor 13.9.;

Figure 3, besidesshowing a plan view of the latheII, also showsschematicallythe circuit for controllingthe. surfacezspeed indicator.I40. Thesurface speed indicator has been shown as a voltmeter which maybe calibrated in. surface;

feet per minute-or some other convenientoalibration showing linearmeasure per unit of time.

A tachometerv genertor HI isshown as being:

driven in accordancenvith the speed Of the spindle shaftiuand'hencegenerates a voltage proportional tothe speed of the spindle "3.; The.

tachometer generator NI is-connected in a series circuit relation withthe surface speed indicator I40 through a. selector switch I42.andresistor meansI IB. The resistor means 143 are-shown as.

a plurality of paralleled resistors each having one end connected-tonneterminal ofthe. ta-

chometer generatorand theotherend connected: The: 'selectorswitch M2 hasa common terminal I44 to a contact on-theselector switch I42.

the volt.- the voltwhich is connected to one terminal of meter I49,and-the other terminal of meter MB is connected to the second terminal.of the tachometer I45 to complete. the circuit,

The resistor means- M3 whichcomprises a plurality of aralleled resistorsprovides varying. amounts'of resistance in the circuit asselected.by-the selector switch Hi2.- The various amountsof resistance in thecircuit correspond to various working diameters of the workpiece ES;selector switch--M2 may be-mounted on-thecontrol panel 84 foi convenientoperation by the.v lathe operator with-;adial-'l45 calibrated'in varioussteps of the working-diameter of the work-- Fourteen steps have-beenshow-n on this dial MS-which; correspondto-the fourteenparalleledresistorsof; the resistor means 443. A:

piece I 9-.

fifteenthposition-isshownand marked R. P. M;

which position-= has been calibrated with suit-'- Thefeed motorrectifier 28 has.

The

, center of the control panel 841 cient' resistance in the: circuit toprovide an indication of. theR..P; M. ofthespindle 18.

The surface speed. indicator I40 offers a great convenience and timesaving to the operator and. set up: man of; the lathe since the operatorneeds only measure the diameter of the workpiece, or the diameter of thetools such as a arm that. is performing work upon the workpiece, andset. the selector switch I42 in the correct position. By knowing thetype of material andtypeof tool the operator may then refer to chartscustomarily used in the trade to obtain the: work. surface cutting speedfor the particular work operation being performed.

With the machine running in a given position,

the operator. may thenmanually adjust one of the knobs. I14. to adjustthe spindle speed and hence the surface cutting speed to the correctvalue-:as observed-on the surface speed indicator I 20. This greatlyrelieves the operator of any calculations in. converting diameter tocircumferenceor determining the peripheral speed for at given diameterin order to correctly use the cutting speed. charts.

Figure 4 shows anxelevational view of the control. panel iiid'whereonallthe electrical controls of the lathe may beconveniently mounted forready accessibility tOLthe lathe operator and set up man. Thiscontrolpanel Gamay be mounted in. any. convenient position at one sideor the hack ofv the. lathe SI, or could be mounted on cabinetiorhousingtherectifiers 2 26, '22 and 2'9. The. first to sixth manualswitches 39 to "I4 are located along. the bottom of the control paneland are shown inthe forward or up position. The reverse-tapping switch75, the cross slide in switchlfi, and the'cross slide out switch H aremounted in a row near the. topof the control panel. Asxpreviouslymentioned, the knobs IE4 control the interlinked armature and fieldpotentiometers for. providing the continuously variable spindlespeeds'in each of the six turret positions. These knobs Il4= are alsoconveniently mounted onithe: control panel in a row near the Six knobsM3 are providedin' a row below the row of knobs Ill. and control thefeed motor potentiometer-s l22to I321for controlling the speed of thefeed motor 23. Pilot lights H17 have been shown to indicate theparticular operating condition of the-lathe and these pilot lights maybe connected across the relays of the control relay means 33 such asindicated on Figure 1 by the pilot light I41? connected across the firstrelay 4?. A feed rate indicator I48shown in the form of a meter may beconveniently mounted on the control paneled-for indicating therate ofspeed of the saddle: I2; This feed rate indicator MS may be suppliedwith"voltage from a tachometer generatordriven from the feed motor whichcircuit arrangement has not been shown.

Thelathe I I is preferably equipped with manua1"as wellas powerfeed ofthe turret it with the powerfeed sele'ctably engageable at the willofx'the lathe operator andthe lathe would then have some form'ofmechanical trip to disengage this power feed at the most forwardmovement of the turret I3 in each'position of the turret l3. Such amechanicaltrip-may be arranged to be actuated-by adjusting screws I 53adjustably mounted on the stop: adjustment teeth I49 to providevariations in the most forward movementnfor each position of the turretl3.

Actuation-of the-reverse pick-up switch 86- sh'ould .beaccomplished:simultaneously with the- 9 actuation of the mechanical tripto disconnect the power feed of the turret I3. Such simultaneousactuation could be accomplished by using a large headed adjusting screwI54 to actuate this reverse pick-up switch 86 as well as the mechanicaltrip for the power feed.

As shown in Figure 3, the rotary tap switch '2I may be mounted on theright hand end of the turret slide for reciprocation therewith, and maybe gear driven to actuate the various tap contacts 35 through 46 thereofin accordance with the rotative position of the turret I3. A flexiblecontrol cable I55 is used to bring the electrical connection from therotary tap switch 2i to the rest of the control circuit 39. In a similarfashion, control cables I53 and I51 carry the electrical connection tothe reverse pick-up switch 85 and the cross slide in and out switches 81and 88.

Operation of the spindle motor The main switch 32 must be closed toprovide energization to the rectifiers 24, 26, 28 and 29 and to thecontrol relay means 33. The first and second time delay relays 56 and 51will be energized assuming that the cross slide I6 is in the neutralposition with the saddle i2 retracted. Assuming that the turret I3 is inthe number one position, the first tap contact 35 of the rotary tapswitch 2I will be actuated to a closed position. Since the first andsecond time delay relays G and 5'?- are energized, the contactors thisand 57A will be closed providing energization to the lead 85. Since apotential difference exists across the leads 85 and 59 and the first tapcontact 35 is closed, the first relay 4? will be energized. Thecorresponding pilot light It? will hence be energized and will providean indication on the control panel 64 that the turret is in the firstposition and that the control circuit is energized ready to provide theoperating conditions to the lathe II. The energization of the firstrelay I'I closes the contactors A to D of this relay. The fieldaccelerating relay 8! has the shunt coil 82 thereof energized to providea slight degree of energization to this relay 8|. The master switch 63,which has been shown as being located in the headstock 55, may then beclosed to provide energization to the forward and reverse relays it and67. The manual switches 69 to 14 have all been shown in the forwardposition and likewise the cross slide in switch it is shown in theforward position. The reverse tapping switch I5 and cross slide outswitch ll have been shown in the reversed position. This will be thenormal position for these switches since one normally desires forwardrotation of the spindle I8 for all positions of the turret and for atool being held on the front part of the cross slide I6. Thus when thecross slide moves inwardly to cause this tool on the front of the crossslide It to perform work upon the workpiece I9, the spindle it shouldrevolve in a forward direction. 'When the cross slide it moves out or,in other words, causes a tool mounted on the back of the cross slide toperform work upon the workpiece I9, then the spindle should rotate in areverse direction. Likewise a reverse rotational direction of thespindle I8 should be provided in order to back a tap out of the work,which tap is held by a chuck in any position of the turret I3. Thisreverse tapping condition may be initiated in any of the positions ofthe turret and may conveniently be effected by pro- 10 viding amechanical actuation of the reverse pick-up switch 86 at the mostforward point of the tap. This reversing of the spindle IB then drivesthe tap out of the workpiece I9.

With the first manual switch 69 in the forward position, the closing ofthe contactor 41A causes energization of the forward relay 66 since thebraking relay contactor !22A is closed. The energization of the forwardrelay 55 closes the contactors 66D and 66E to provide energization tosaid spindle motor armature 25 in a direction to cause forward rotationof the spindle motor 22. Also the contactor 960 is opened to release thedynamic braking resistance I2I from its connection across the armature25. The contactor 66B is opened to prevent the short circuit across thecontrol leads H5 and H5 of the field rectifier 26; hence causing theoutput voltage of this field rectifier 26 to be controlled by the fieldpotentiometer 95 since the contactor 41B is closed. The spindle motor 22hence comes up to a speed dictated by the settings of the field andarmature potentiometers 95 and I05 since the contactor HC is closed toprovide control of the armature rectifier 24 by the armaturepotentiometer I95. The contactor 66A closes to cause energization of thebraking control relay 80. The energization of this braking control relay$5 closes the contactor A thereof which shunts the second holdingresistor I23. The second holding resistor I23 has a resistance valuesufilcient to prevent pull in of the braking relay I22 upon subjectionof the series combination of the second holding resistor I23 and thebraking relay I 22 to the rated armature voltage. The resistance valueof the second holding resistor I23 also is insufficient to cause dropout of the braking relay I22 upon energization and pull in thereof. Theclosing of the contactor 80A and the shunting of this second holdingresistor I23 then provides for the energization of the braking relay I22with a consequent opening of the contactor I22A. This braking relaycontactor I 22A, upon being opened, does not cause drop out of theforward relay 66 since the first holding resistor I9 does not have aresistance value, with a corresponding voltage drop, of sufficientvalue.

The invention provides for a quick change of speed between one operatingcondition and the next, such as between the first and second positionsof the turret. The braking system provides for such quick change ofspeed in the following manner: Assuming that the turret is to be changedfrom the first to the second position, the rotary tap switch 2| willthen cause actuation of the third tap contact 3! in this position and inso moving to this second position of the turret, the second tap contact33 will be actuated. Before the third tap contact 3'! is actuated, thefirst tap contact 35 will be de-actuated to the open condition, Thisde-energizes the first relay 4! opening all contactors thereof.

Opening the contactors 47B and 41C releases the field and armaturerectifiers 26 and 24 from the control of the field and armaturepotentiometers and I05. The opening of the contactor 41A drops out theforward relay 66 opening the contactors 66D and 66E and closing thecontactor 56C to provide dynamic braking of the spindle motor armature25 through the dynamic braking resistance I2 I. The contactor 65B closesto provide full field excitation of the field 21 to aid this dynamicbraking. The contactor 66A opens to drop out the braking control relay80 and opens the contactor 86A thereof. This places the second holdingresistance 23 in series with the braking relay 322 and since this secondholding resistance I23 will have a voltage drop thercacrc-ss, thebraking relay :22 will drop out at a much hig' er armature voltage thanif that braking relay 522 were to be connected directly across thearmature 25. Thus the second holding resistor i23 provides an adjustmentfor the minimum s eed to which the spindle motor 22 is braked duringchange between one operating condition and the next. Since the voltageon which the ordinary relay will hold in is considerabl" lower than thepull in voltage or especially the rated voltage thereof, approximately20-25 per cen this second holding resistor I23 thereby provide acalculated change in the drop out voltage or the br king relay 22.

When te braking relay l22 drops out, the contactor K321i holding resitor this time, the third tap contact will have been closed by theindexing of the turret 53 to the second position thereof and hence thesecond relay is will have been pulled in to close the four contactorsthereof. With the contactor 48A closed and the second manual switch toin the forward position, the forward relay St will then be energizedsuffi ciently to pull in upon the closing of the braking relay contactor22A The cycle of operation as previously described will then beduplicated. In other words, the spindle motor 22 will up to speeddictated by the settings of the field and armature potentiometers andE65. Also, the

braking control relay 33 will be energized, en-

ergizing the braking relay i722 to open the contactor 522A thereof. Sucha process of braking to a pre-determined speed and re-accelerating tothe new speed condition will be accomplished each time the turret i3 isindexed to a new operative position.

The operation of the circuit as governed by the reverse pick-up switch85 may be accomplished in any operative condition of the lathe whereinthe spindle i8 is rotating in a reverse direction. For instance, oneposition of the turret l3 may be to drill a hole in the workpiece i9 andthe next operative position of the turret may be to tap threads on theinternal bore of this hole. tom of the hole a mechanical trip may becaused to actuate the reverse pick-up switch 33 in any position of theturret l3 and would be set to so trip this reverse pick-up switch 83 atthe instant of completion of the tapping operation.

This reverse pick-up switch 36 then contacts the upper contact thereofto energize the reverse tapping relay 53. The contactor 553D thereofcloses as a holding contactor to keep this reverse tapping relay 53energized. The contactor 53E thereupon opens to prevent control of theoperation of the lathe by any of the first to sixth relays to 52. Theopening of the contactor 53E thereupon causes de-energization of thesecond relay 4G or whichever of the first to sixth relays a? to 52 is atthat time effecting control of the lathe. This de-energization of one ofthe first to sixth relays will cause a de-energization of the forwardrelay S6 and hence the spindle motor 22 will be dynamically braked. Thecontactor 53A closes and with the reverse tapping switch '55 in thereverse position, the reverse lead Si is energized to energize thereverse relay 6?. The energization of this reverse relay 81 performs acycle of operation similar to the operathereor closes to shunt the firstWhen the tap has reached the bot- F tion performed by the energizationof the forward relay 58. The reverse relay contactors 51D and 61E closeto energize the spindle armature 25 in a reverse direction. Thecontactor 67C opens to relieve the spindle motor armature 25 from itsdynamic braking action. The contactor 51B opens to release the shortacross the control leads H5 and H6 and place the field rectifier 25under the control of the field potentiometer It! i. The armaturerectifier 2 will be under the control of the armature potentiometer IH,since the contactor 530 will be closed. The spindle motor 22 will thencome up to a reverse rotational speed dictated by the setting of theknob i M which simultaneously governs the position of the movablefingers on the potentiometers IQ! and l l l. The closing of thecontactor 67A causes energization of the braking control relay 3D toclose the contactor 88A thereof and hence cause energization of thebraking relay I22 which opens the contactor I22A. The circuit is then inthe stable running condition with the spindle motor 22 running in areverse direction to back the tap from the workpiece I 9.

The even-numbered tap contacts 36, 33, 40, 42, 4a and is are allconnected to the lead 89 which is provided to energize the third timedelay relay 523. As is conventional practice, the turret is indexed tothe next position thereof upon a complete retraction of the saddle :2.As previously stated, during this indexing, one of the even-numbered tapcontacts will be actuated to the closed position. For instance, if thetap had been held by a chuck on the fifth position of the turret it,then the reverse tapping condition would have been initiated at the endof this tapping operation and during the indexing from the fifth to thesixth position, the tenth tap contact 4? would have been actuated tocause energization of the lead 89, hence energizing the third time delayrelay 58. Such energization opens the contactor 55A to drop out thereverse tapping relay 53. Since this opens the contactor 53A, thereverse relay 6? drops out and the spindle motor 22 is dynamicallybraked. When the eleventh tap contact Z5 is energized, and after thebraking relay contactor 122A closes, the sixth relay 52 will beenergized to close the four contacts thereof. When the contactor 52Acloses, the forward relay 65 will be energized just as soon as thebraking relay contactor lZEA closes, to resume forward rotation of thespindle motor 22 under control of the potentiometers E50 and HG.

It will be seen that the reverse tapping operation can be used after anyof the six operative positions of the turret l3 and the circuit willprovide for a resumption of forward rotation after this reverse rotationsince there is even-numbered tap contact between each odd-numberedcontact that establishes the operative condition for each of thepositions of the turret H3.

The cross slide in and cross slide out positions are provided so thatcontinuously variable spindle speeds may be effected to vary the surfacecutting speed when the workpiece i9 is being Worked by a tool held oneither the front or the back of the cross slide 15. The cross slide incondition may be controlled in spindle speed by the knob I50, shown onthe control panel 64 in Figure 4, which controls simultaneously andcomplementarily the potentiometers I62 and H2. The cross slide outcondition may be controlled in spindle speed by the knob l5! which in asimilar fashion controls the potentiometers I03 and H3. The knob I52 maybe used to control the spindle speed during the reverse tappingcondition. When the lathe condition is being controlled by one of thefirst to sixth relays 41 to 52, the reverse pick-up switch 86 is in thenormal or lower position which causes energization of the first andsecond time delay relays 56 and 51. Initial movement of the cross slideI6 either in or out will cause actuation of the respective cross slidein or cross slide out switch 81 or 88. For an inward movement of thecross slide IS, the cross slide in switch 81 will be actuated to thelower position causing drop out of the first time delay relay 56. Theopening of the contactor 56A prevents control of the lathe by any of thefirst to sixth relays 47 to 52 hence dropping out the forward or reverserelay B6 or 61, whichever had previously been actuated to dynamicallybrake the spindle motor 22. The contactor 56D closes to provideenergization of the cross slide in relay 54 with consequent closing ofthe four contactors A to D thereof. The closing of the contactor 54Dpermits current to flow through the line 6 I, the corn tactor 54D, theconnecting lead 92, the second time delay contactor 510, the connectinglead 93, the cross slide in contactor 54A, the cross slide in switch I6and the forward lead 90 to energize the forward relay 65. The spindlemotor 22 will then come up to a speed dictated by the settings of thepotentiometers I02 and H2. When the cross slide is returned to thenormal position, the cross slide in switch 8'! will be returned to thenormal or upper position to drop out the cross slide in relay 54 and tore-energize the first time delay relay 56. The opening of the contactors2D and 54A drops out the forward relay 66 and dynamically brakes thespindle motor 22. Should the cross slide be moved outwardly, the crossslide out switch 88 would be actuated, de-energizing the second timedelay relay 51, closing contactor 51B to energize the cross slide outrelay 55, Current would then flow from the control rectifier 29 throughthe a lead BI, the first time delay relay contactor 560, the connectinglead 92, the cross slide out contactor 551), the connecting lead 93, thecross slide out contactor the cross slide out switch 11, and the reverselead 9| to energize the reverse relay 61 upon the close of the brakingrelay contactor I22A. The spindle motor 22 will hence come up to areverse rotational speed dictated by the settings of the potentiometersI 03 and I I3.

The lower contacts of the single pole, double throw cross slide in andout switches 81 and 83 are connected to the lead 89 for energizationthereof upon the actuation of either of these cross slide switches toenergize the third time delay relay 58 and hence drop out the reversetapping relay 53 should it happen to be energized. Thus, the movement ofthe cross slide I6 either in or out will cause drop out of the reversetapping condition in the same fashion as the indexing to a new positionof the turret I3 with consequent actuation of any of the evennumberedtap contacts on the rotary tap switch 2I.

The field accelerating relay 8| comes into play when the spindle motor22 is to be accelerated to some speed above base speed. The armaturerectifier 24 will be attempting under this condition, to supply a heavycurrent to the armature to accomplish this increase in speed 14 sincethe field 21 will have a low excitation. Such a heavy inrush of currentwill go through the series field accelerating coil 83 and the lines offlux established in the core thereby, aided by the shunt coil 82, willcause a pull in of this field accelerating relay Hi. The contactor 8IAwill thereby become closed to short the control leads H5 and H6 toprovide full excitation to the field 21, This closing of the contactor8IA relieves this field rectifier 26 from whichever field potentiometernormally has control in that particular operative condition of thelathe. When the field 21 receives this full excitation, the rush ofcurrent from the armature rectifier 24 will be diminished since thespindle motor 22 will no longer be under this accelerating influence.The

series coil 83 will therefore add very few flux lines to the core of thefield accelerating relay '8I and hence this relay will drop out to openthe contactor 8| A thereof. The field rectifier 25 will therefore againbe placed under control of speed above base speed. This again will causea heavy inrush of current to the armature 25 to pull in the fieldaccelerating relay 8|. This cycle of operation may continue for a numberof cycles with the field accelerating relay chattering until the spindlemotor 22 is accelerated to the correct speed. The purpose of the fieldaccelerating relay 8| is to prevent a heavy inrush of current to thearmature and is in the nature of a protective device to protect the arcdischarge devices of the armature rectifier from heavy overloads. Thisis a superior method of overload protection for it does not cause adisruption in the operation of the lathe and permits the spindle motor22 to accelerate to the pre-set speed above base speed as rapidly and atas high a current rating as the arc discharge devices of the armaturerectifier 24 will safely permit.

Operation of the feed motor The feed motor 23 is adapted to becontrolled through a continuously variable speed range to providecontinuously variable rates of speed of the turret I3. This permitsoptimum operating condition of the lathe for any particular cut or workoperation on the workpiece I9. When the main switch 32 is closed, thefeed motor rectifier 28 will be energized, also the leads 59 and 60 willbe energized to cause energization and pull in of the first and secondtime delay relays 56 and 51 and the consequent closing of the contactors56B and 51B thereof will permit energization of the feed motor relayI35. When the master switch 63 is closed, the output voltage from thecontrol rectifier 29 will be applied through one of the first to sixthrelay contactors to the forward lead 90, and since the contactors 56Band 51B are closed, the feed motor relay I35 will become energized sincethe feed brake relay contactor I38A is closed. The third holdingresistor I39 has a resistance value sufiicient to prevent pull of thefeed motor relay I 35 upon subjection of this series combination to thecontrol voltage from the control rectifier 29. The resistance value ofthis third holding resistor I39 is, however, insufficient to cause dropout of the feed motor relay I 35 after energizetion and pull in thereof,such as can be effected by shunting the third holding resistor I39. Theenergization of the feed motor relay I 35 opens the contactors C and Dto release the feed motor 23 from its dynamic braking condition. Thecontactors I35A and I35B close to provide energization to this feedmotor 23 from the feed motor rectifier 28 with the field I31 andarmature I38 connected in series. The feed motor 23 will then come up tospeed dictated by the setting of whichever feed motor potentiometer I21through I32 that is in control at that time. For instance, if the turretI3 is in the first position, the first relay 4'! will be energizedclosing the contactor 41D and permitting the feed motor potentiometerI21 to control the output voltage of the feed motor rectifier 28. Thefeed brake relay I38 will energize by normal armature voltage and willcause opening of the contactor I38A thereof. This relieves the shuntacross the third holding resistor I39, however, the feed motor relay I35still holds in. Upon a changing of the turret to the next operativeposition, a new feed rate of the turret I3 may be desired and hence maybe controlled by the setting of the appropriate feed motorpotentiometer, in this case the potentiometer I28. When the turret I3 isindexed to this next position, which in this example is the secondposition, the first relay il will drop out opening the contactor 41Dhence placing an infinite impedance across the control leads I24 and I25to cause the output voltage of the feed motor rectifier 28 to drop to aminimum value. The drop out of the first relay 4'! will open thecontactor 41A de-energizing the forward lead 90 and hence dropping outthe feed motor relay I35. The contactors I35A and B open and thecontactors 535C and D close to provide dynamic braking to the feed motorwith the field I31 reversed from the con-- nection during the runningcondition. The feed motor 23 is hence rapidly braked to a stop. The feedbrake relay I38, which is dependent upon the voltage across the armatureI36, will hold in until the voltage across this armature 535 has droppedto the drop out voltage value of this feed brake relay I38. This permitstime for the dynamic braking of the feed motor 23 before the closing ofthe contactors I38A will permit the feed motor relay I35 to again pullin. Upon pull in of this feed motor relay I35, the dynamic brakingcondition of the feed motor 23 is released and it is reconnected to thefeed motor rectifier I28 and will come up to a speed dictated by thesetting of the second feed motor potentiometer I28.

What is claimed is:

1. In a turret lathe having a spindle and a turret with a given numberof indeXable positions, drive means for driving said spindle,energization means connected in circuit with said drive means, means forcontrolling the energization supplied to said drive means and includingmovable switch means driven in accordance with the rotation of saidturret, said movable switch means having twice said given number ofpositions, the odd numbered positions corresponding to the said givennumber of indexable positions of said turret to provide difierent speedconditions for each of said indexable positions, reversing means forproviding reversal of said spindle, and circuit means controlled by theeven numbered positions providing for relieving the reverse rotation ofsaid spindle under the control of said reversing means.

2. In a turret lathe having a spindle and a turret with a given numberof indexable positions a spindle motor, drive means for energizing saidspindle motor, control means for providing variable amounts ofenergization of said drive means to provide varying speeds to saidspindle motor, said control means including a switch driven inaccordance with the position of said turret, said switch having twicesaid given number of positions with the odd-numbered positions thereofcorresponding to said given number of indexable positions of saidturret, connection means interconnecting said odd-numbered positions ofsaid switch and said control means to provide different amounts ofenergization of said drive means and hence providing different spindlespeed conditions in each indexable position, a reversing switch for atleast one of said indexable positions to provide reversed rotation ofsaid spindle motor, and circuits connected to the even-numberedpositions of said switch providing for relieving the reverse rotation ofsaid spindle under the control of said reversing switch.

3. In a turret lathe having a spindle and a turret with a given numberof indexable positions, a spindle motor, drive means for energizing saidspindle motor, control means for providing variable amounts ofenergication of said drive means to provide varying speeds to saidspindle motor, said control including a switch driven in accordance withthe position of said turret, said switch having twice said given numoerof positions and having at least one electrical contact for eachposition with the alternate positions thereof and correspondingelectrical contacts corresponding to said given number of indexablepositions of said turret, circuits interconnecting said electricalcontacts corresponding to alternate positions of said switch and saidcontrol means to provide difierent amounts of energization of said drivemeans and hence providing different spindle speed conditions in eachind-enable position, reversing means for reversing the rotation of saidspindle motor, and means interconnecting the other positions of saidrotary switch and said control means for relieving the controlestablished by said reversing means.

4.. In a turret lathe having a spindle and a slidable saddle, a turretrotatively mounted thereon and having a given number of indexablepositions, a spindle motor, drive means for energizing said spindlemotor, control means for providing variable amounts of energization ofsaid drive means to provide varying speeds to said spindle motor, saidcontrol means including a contact carrying switch operated in accordancewith the position of said turret, said switch having twice said givennumber of positions with the alternate positions thereof correspondingto said given number of indexable positions of said turret, electriccircuit means interconnectin said alternate positions of said rotaryswitch and said control means to provide different amounts ofenergization or" said drive means and hence providing in one of saidxable positions by said slidable movement of said saddle to reverse therotation of said spindle motor and to render inefiective the controlestablished by all of said alternate positions, and means controlled bythe other positions of said rotary switch for providing cessation ofreverse rotation of said spindle motor.

5. In a turret lathe having a spindle and a slidable saddle, a turretmounted on said saddle and having six rotative indexable positions, aspindle motor, drive means for energizing said spindle motor, controlmeans including variable means for controlling the degree ofenergization of said drive means to provide varying speeds to saidspindle motor, said control means including a rotary switch rotated inaccordance with the rotation of said turret, said rotary switch having acontactor in each of twelve positions with the odd-numbered contactorsthereof corresponding to said six indexable positions of said turret,six indexing relays each energizable by the actuation of one of saidodd-numbered contactors respectively, connection means interconnectingsaid odd-numbered contactors of said rotary switch and said variablemeans of said control means to provide variable forward rotationalspeeds of said spindle motor in each of said indexable positions, areverse pick-up switch actuable by said slidable movement of said saddlewith said turret in one of said indexable positions, a reverse relayenergizable by the actuation of said reverse pick-up switch to providereverse rotation of said spindle motor, a reverse control contactor onsaid reverse relay to de-energize all of said indexing relays and hencerender inelfective the control established thereby, and a forwardcontrol relay energizable upon actuation of any of the even-numberedcontactors of said rotary switch for deenergizing said reverse relay tothereby condition said control means for forward rotation of saidspindle motor under the control of one of said six indexing relays.

6. A control circuit for a turret lathe having a spindle motor, saidspindle motor having an armature, armature energization means capable ofenergizing said armature, control relay means for energizing saidspindle motor upon being energized, dynamic braking means includingmeans for disconnecting said armature energization means from saidarmature and contact means for connecting a dynamic braking resistancethereacross, control voltage means capable of energizing said controlrelay means, a first holding resistor connected in series with saidcontrol relay means and having a resistance value sufiicient to preventpull-in of said control relay means upon subjection of said seriescombination to said control voltage and insuificient to cause drop-outof said control relay means after pull-in thereof, a, braking relay anda second holding resistor serially connected across said armature withsaid second holding resistor having a resistance value suiiicient toprevent pull-in of said braking relay on normal armature voltage appliedto said last named series combination and insuificient to cause drop-outof said braking relay on normal armature voltage after said brakingrelay has been. energized, a normally closed braking relay contactorbridging said first holding resi tor, a braking control relay, means forenergizing said braking control relay upon energization of said armaturefrom said armature energization means, and a normally open brakingcontrol relay contactor bridging said second holding resistor.

'7. A control circuit for a turret lathe having a spindle motor, saidspindle motor having an armature, an armature rectifier for supplyingrectified A. C. power to' said armature, control means for controllingthe energization of said spindle motor, said control means includingswitch means, control relay means energizable by said switch means,dynamic braking means in cluding means for disconnecting said armaturerectifier from said armature and contact means for connecting a dynamicbraking resistance thereacross, control voltage means'capable ofenergizing said control relay means, a first holding resistor connectedin series with said control relay means and having a resistance valuesufiicient to prevent pull-in of said control relay means uponsubjection of said series combination to said control voltage andinsuiiicient to cause drop-out of said control relay means after pullinthereof, a braking relay and a second holding resistor seriallyconnected across said armature with said second holding resistor havinga resistance value sufiicient to prevent pull-in of said braking relayon normal armature voltage applied to said last named series combinationand insufficient to cause drop-out of said braking relay on normalarmature voltage after said braking relay has been energized, a normallyclosed bra-king relay contactor bridging said first holding resistor, abraking control relay, means for energizing said braking control relayupon energization of said armature from said armature rectifier, and anormally open braking control relay contactor bridging said secondholding resistor.

8. A control circuit for a turret lathe having a spindle motor, saidspindle motor having an i viding variable speeds to said spindle motor,forward and reverse relays selectably energizable by said switch means,dynamic braking means including means for disconnecting said armaturerectifier from said armature and contact means for connecting a dynamicbraking resistance thereacross, control voltage means capable ofenergizing said forward or reverse relays, a first holding resistorconnected in series with said forward and reverse relays and having aresistance value sufiicient to prevent pull-in of said relays uponsubjection of said series combination to said control voltage andinsuiiicient to cause drop-out of said relays after one of said relayshas pulled in, a braking relay and a second holding resistor seriallyconnected across said armature with said second. holding resistor havinga resistance value sunicient to prevent pull-in of said braking relay onnormal armature voltage applied to said last named series combinationand insufficient to cause drop-out of said braking relay on normalarmature voltage after said braking relay has been energized, a normallyclosed braking relay contactor bridging said first holding resistor, abraking control relay, means for energizing said braking control relayupon energization of said armature from saidarmature rectifier, and anormally open braking control relay contactor bridging said secondholding resistor.

9,. A control circuit for a turret lathe having a spindle motor, saidspindle motor having a field winding and an armature, an armaturerectifier for supplying rectified A. C. power to said armature, a fieldrectiiierior supplying rectified A. C. power to said field winding, asaddle slidable on said lathe, a turret mounted on said saddle andhaving six indexable positions, control means for controlling theenergization of said spindle motor and hence the speed thereof, saidcontrol means including switch means having six conditions correspondingto said six 'indexable positions of said turret for providing variablespeeds to said-spindle motor in each of said indexable positions,forward and reverse relays selectably energizable by said switch meansin any of said six conditions for providing forward or reverse rotationof said spindle motor, dynamic braking means including means fordisconnecting said armature rectifier from said armature and contactmeans for connecting a dynamic braking resistance thereacross, controlvoltage means capable of energizing said forward or reverse relays, afirst holding resistor connected in series with said forward and reverserelays and having a. resistance value sufficient to prevent pull-in ofsaid relays upon subjection of said series combination to said controlvoltage and insufiicient to cause drop-out of said relays after one ofsaid relays has pulled-in, a braking relay and a second holding resistorserially connected across said armature with said second holdingresistor having a resistance value sufficient to prevent pull-in of saidbraking relay on normal armature voltage applied to said last namedseries combination and insufficient to cause drop-out of said brakingrelay on normal armature voltage after said braking relay has beenenergized, a normally closed braking relay contactor bridging said firstholding resistor, a braking control relay, means for energizing saidbraking control relay upon energization of said armature from saidarmature rectifier, and a normally open braking control relay contactorbridging said second holding resistor.

10. A turret lathe having a spindle motor with an armature, power meansfor supplying power to said armature, a turret mounted on said lathe andhaving a given number of indexable positions, control means forcontrolling the energization supplied by said power means to said spin:dle motor and hence the speed thereof, said control means includingindexing switch means actuated in accordance with the position of saidturret, said indexing switch means having twice said given number ofcontact positions with the odd-numbered positions thereof correspondingto said given number of indexable positions of said turret, a forwardrelay, connection means interconnecting said odd-numbered contactpositions of said indexing switch means and said forward relay forenergization thereof to provide forward rotation of said spindle motorin each of said indexable positions, a reverse relay, means forenergizing said reverse relay to provide a reverse rotation of saidspindle motor and to render ineffective the control established by saidforward relay, forward control means energizable upon actuation of anyof the even-numbered positions of said indexing switch means forde-energizing said reverse relay to thereby restore the spindle motor tothe control of said odd-numbered positions of said indexing switchmeans, dynamic braking means for dynamically braking said spindle motorduring movement of said turret from one indexing position to another,said dynamic braking means including means for disconnecting said powermeans from said armature and connecting a dynamic braking resistancethereacross, control voltage means capable of energizing said forwardand reverse relays, a first holding resistor serially comiected to saidforward and reverse relays, said first holding resistor having aresistance value sufficient to prevent pull-in of either of said forwardor reverse relays upon subjection of said series combination to saidcontrol voltage and insufiicient to cause drop-out of said relays afterone of said forward or reverse relays has pulled in, a braking relay anda second holding resistor serially connected across said armature withsaid second holding resistor have ing a resistance value sufficient toprevent pull-in of said braking relay on normal armature voltage appliedto said last named series combination and insufficient to cause drop-outof said braking relay on normal armature voltage after said brakingrelay has been energized, a normally closed braking relay contactorbridging said first holding resistor, a braking control relay, mean forenergizing said braking control relay upon energization of said armaturefrom said power means, and a normally open braking control relaycontactor bridging said second holding resistor.

11. A turret lathe having a spindle motor with an armature, an armaturerectifier for supplying rectified A. C. power to said armature, a saddleslidable on said lathe, a turret mounted on said saddle and having sixindexable positions, control means for controlling the energization ofsaid spindle motor and hence the speed thereof, said control meansincluding a rotary switch rotated in accordance with the rotation ofsaid turret, said rotary switch having a contactor in each of twelvepositions with the odd-numbered contactors thereof corresponding to saidsix indexable positions of said turret, six indexing relays eachenergizable by the actuation of one of said odd-numbered contactors,respectively, a forward relay energizable by the energization of any ofsaid six indexing relays to provide forward rotation of said sp ndlemotor, connection means interconnecting said odd-numbered contactors ofsaid rotary switch and said control means to provide variable forwardrotational speeds of said spindle motor in each of said indexablepositions, a reverse pick-up switch actuable by said slidable movementof said saddle with said turret in one of said indexable positions, areverse relay energizable by the actuation of said reverse pick-upswitch to provide reverse rotation of said spindle motor, a reversecontrol contactor on said reverse relay to de-energize all of saidindexing relays and hence render ineffective the control establishedthereby, a release control relay energizable upon actuation of any ofthe even-numbered contactors of said rotary switch for deenergizing saidreverse relay to thereby condition said control means for forwardrotational direction of said spindle motor under the control of one ofsaid six indexing relays, dynamic braking means for dynamically brakingsaid spindle motor during the time when neither forward nor reverserelays are energized, said dynamic brake ing means including means fordisconnecting said armature and connecting a dynamic braking resistancethereacross, control voltage means capable of energizing said forward orreverse relays, a first holding resistor serially connected with saidforward and reverse relays and having a resistance value suflicient toprevent pull-in of either of said relays upon subjection of said se riescombination to said control voltage and insufiicient to cause drop-outof said relays after one of said forward or reverse relays has pulledin, a braking relay and a second holding resistor serially connectedacross said armature with said second holding resistor having aresistance va ue sufiicient to prevent pull-in of said braking relay onnormal armature voltage applied to said last named series combinationand insufficient to cause drop-out of said braking relay on normalarmature voltage after said braking relay has been energized, a normallyclosed braking relay contactor bridging said first holding resistor, abraking control relay, means for energizing said 21 braking controlrelay upon energization of said armature from said armature rectifier,and a normally open braking control relay contactor bridging said secondholding resistor.

12. A motor, a rotatable member with a given number of indexablepositions, energization means connected in circuit with said motor forcontrolling the energization supplied to said motor and includingmovable switch means driven in accordance with the rotation of saidrotatable member, said movable switch means having twice said givennumber of positions, the odd numbered positions corresponding to thesaid given number of indexable positions of said rotatable member toprovide different speed conditions for each of said indexable positions,reversing means for providing reversal of said motor, and circuit meanscontrolled by the even numbered positions providing for relieving thereverse rotation of said motor under the control of said reversingmeans.

13. A motor, a rotatable member with a given number of indexablepositions, drive means for energizing said motor, control means forproviding variable amounts of energization of said drive means toprovide varying speeds to said motor, said control means including aswitch driven in accordance with the position of said rotatable member,said switch having twice said given number of positions with theodd-numbered positions thereof corresponding to said given numher ofindexable positions of said rotatable member, connection meansinterconnecting said oddnu mbered positions of said switch and saidcontrol means to provide diiferent amounts of energization of said drivemeans and hence providing different motor speed conditions in eachindexible position, a reversing switch for at least one of saidindexable positions to provide reversed rotation of said motor, andcircuits connected to the even-numbered positions of said switchproviding for relieving the reverse rotation of said motor under thecontrol of said reversing switch.

CLAUDE. E. GREENE.

ROBERT B. LESHER.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,193,258 Gorman Aug. 1, 1916 1,269,489 Murphy June 11, 19181,551,860 Yingling Sept. 1, 1925 1,709,674 Kuhl Apr. 16, 1929 1,934,506King et al Nov. 7, 1933 2,209,037 Riegger July 23, 1940 2,338,599Ridgway Jan. 4, 1944 2,376,552 Nelson et al May 22, 1945 2,405,686 ClarkAug. 13, 1946 2,415,492 Hines Feb. 11, 1947 2,542,421 McClelland Feb.20, 1951

